by anthozoan species
6.1. Mediterranean gorgonian forests. . . . 43 6.2. Sea pen dominated communities. . . . 44 6.3. Mediterranean black coral gardens . . . . 45 6.4. Mediterranean cold water coral reefs and frameworks. . . . 46
Life in a Mediterranean gorgonian forest. © Frhojdysz | Dreamstime.com.
species as well as the need of management actions to ensure the gorgonians viability in the face of global change.
Similarly, bamboo coral forests seem to thrive only in certain areas and the loss of these unique habitats comes accompanied by a great ecosystemic and biodiversity loss of pelagic or demersal species that gravitate around these habitats.
6.2. Sea pen dominated communities
Due to their distribution on muddy and sandy bottoms, and also occasionally on cobbles and rhodolith beds, these species are especially vulnerable to human activities. Many of the most destructive anthropogenic activities, including trawl fishing, oil drilling, sand extraction, waste dumping, etc., occur on and over the beds where they live.
These habitats are considered key sites of aggregation for biodiversity, also supporting a high abundance of species of commercial interest. For example, the tall sea pen (F.
quadrangularis) beds are considered Essential and Sensitive Habitats (Essential Fish Habitats, EFH) by the General Fisheries Commission for the Mediterranean (GFCM) and the European Commission, due to their fragility and importance for commercial species of crustaceans, such as the Norway
Lobster (Nephrops norvegicus) and the deep-sea Rose Shrimp (Parapenaeus longirostris). The Barcelona Convention includes Pennatula beds as unique formations of Conservation Interest under the “Dark Habitats” Mediterranean Action Plan.
The impacts of human activities, particularly the increase in fishing practices over bottoms with pennatulaceans, have provoked sharp declines in several species. It is inferred that F. quadrangularis, P. phosphorea, P. rubra and P. spinosum populations in the Mediterranean Sea have decreased by around 40% in the last 20 years and it is expected that this trend will continue in the future.
It is necessary to develop protection plans to avoid the continued degradation and loss of sea pen aggregations, and of the biodiversity that they host. These measures would also imply benefits for Mediterranean commercial fisheries, by protecting Essential Habitats for crustaceans and fishes that spend part of their life cycle in these valuable habitats.
The creation of Marine Protected Areas in the sites where the densest aggregations of sea pens occur, the inclusion of these species in the annexes of the Specially Protected Areas and Biological Diversity in the Mediterranean SP/BD Protocol, together with their recognition as Vulnerable Marine Habitats within the GFCM, will help to stop their decreasing trend and the loss of these important species and communities.
Funiculina quadrangularis in Giannutri Island, Punta Secca, 104 m depth. © Simone Nicoli.
6.3. Mediterranean black coral gardens
The use of ROVs is rapidly reducing the knowledge gap on the distribution of deep Mediterranean black coral species and we know today that black corals are far more common than was thought in the past. ROV exploration is however also proving that the structure and distribution of the existing assemblages may represent a reduction in their original natural abundance.
Numerous anthropogenic threats have been recognized for the Mediterranean antipatharian fauna, but the effects of fishing (direct and indirect) are probably the most important. Bottom longlining is generally practiced in untrawlable rocky areas that are good habitats for black corals. These species, due to their tendency to form dense aggregations, to their size and their tree-like morphology, have an increased catchability. In addition, specimens may also be damaged in situ by fishing. The most significant impact on the colonies is mechanical damage, their entanglement and the resuspension of nearby soft sediments which may choke them over time. Damaged colonies are also more susceptible to the colonization of epibiont organisms that slowly increase their mortality (Bo et al. 2014, 2015).
The available information from fisheries by-catch as well as the ROV observations have informed the decision to list A. subpinnata, A. dichotoma and P. larix as Near Threatened species due to an inferred population reduction of about 20%.
Contributing factors include the current distribution of the subpopulations, their current health status, the observed decline in the habitat quality, the biological factors enhancing their catchability and reduced recovery ability, as well as the continuous existing fishing pressure on deep hard grounds. A more severe situation has been inferred for L. glaberrima, listed as Endangered due to a decline in the population of about 50%
over 100 years due to the millennial life span of this species.
Other pressures to black corals include direct harvesting for jewelry, particularly well documented historically in France, Cyprus, Croatia, Morocco and especially Malta in the 1980s (Deidun et al. 2010). Further, deep mass mortality events are known to occur, but are not well known. Other pressures such as sea floor drilling for oil exploration or future mining can and will threaten the integrity of these deep benthic communities.
There is an urgent need for basin-scale management measures focused on the protection of the black coral assemblages as well as a communication plan targeting fishermen and ultimate users to explain the importance of these marine communities. Further actions need to focus on a comprehensive census of the distribution of the deep populations in the Mediterranean basin, increase the knowledge on the biological and ecological characteristics of these species, and identify and designate MPAs with strict fishing restrictions in order to conserve black coral populations.
Leiopathes glaberrima from Carloforte shoal (Sardinia, Italy). © Marzia Bo (UNIGE) & Simonepietro Canese (ISPRA).
6.4. Mediterranean cold water coral reefs and frameworks
Mediterranean cold water coral reefs and frameworks constitute one of the most vulnerable marine ecosystems. Their current distribution, limited to some special areas where they find suitable environmental conditions but also locations which are under anthropogenic impact, demand protection and an adequate management of activities in these areas where they develop.
The available information regarding the current status of the Mediterranean deep water coral populations of Lophelia pertusa and Madrepora oculata indicate a 40-50% decline over the last 50-60 years, mostly due to bottom trawling, although other fisheries practices such as benthic longline and gill net gears used at the submarine canyons represent additional threats (Orejas et al. 2009). Climate change, ocean acidification and fishing impacts, together with their slow growth rates, clearly indicate that damage to these communities would have dramatic consequences for the ecosystem and recovery will take a long time (or may even be irreversible) for these deep water communities.
Several investigations based on aquarium experiments have been published on the potential effects of ocean acidification in cold water coral species in the Mediterranean, and responses seem to be species specific and also highly dependent on the exposure regime (e.g. Maier et al. 2013 and references therein, Carreiro-Silva et al. 2014, Movilla et al. 2014a,b, Rodolfo-Metalpa et al. 2015). These studies suggest some degree of acclimation to changes in carbonate chemistry and the long term effects of ocean acidification, but also different types and degrees of impacts on calcification and respiration rates and effects on the skeletal structure that could result in weakening or additional mechanical damage to the reef frameworks.
Given this uncertainty, the precautionary declaration of protection areas and adoption of good management measures should be implemented and replicated at different locations in the Mediterranean to protect these ecosystems.
Additional scientific studies are also essential if we are to understand better the ecology of deep sea corals and their communities to use this information as a tool to legislate and manage the marine environment in a sustainable manner.
Dendrophyllia cornigera off Malaga coast, Spain. © OCEANA.
This report presents the first comprehensive regional IUCN Red List assessment of the anthozoan fauna of the Mediterranean region, with 17 (12.6 %) out of 136 species considered to be threatened. Of these, 1 is Critically Endangered (0.7% of the total), 9 are Endangered (6.7%), and 7 are Vulnerable (5.2%).
Due to insufficient knowledge and information, 69 (51%) of the assessed species are listed as being Data Deficient in the Mediterranean region. Ten species (7.4%) were listed as Near Threatened, and 40 (29%) were listed as Least Concern.
Increased funding and research attention thus needs to be directed towards both the 17 Threatened species and the 69 Data Deficient species, and particularly the 19 endemic species that are Data Deficient species. More research and survey efforts are need in the south of the Mediterranean including the Levantine Sea, North Africa and deeper waters to fill the data gaps. In particular, more research and survey efforts are needed in the south of the Mediterranean including the Levantine Sea, North Africa and deeper waters.
This is particularly important when there are apparent threats yet virtually no available data on population sizes or biological parameters.
In addition, not all taxonomic groups from the different regions in the Mediterranean have been well investigated and currently undescribed species are expected to be discovered in coming years. Assessing the recently recognized species (Appendix 2) and revising the list of threatened species regularly with the new information available will help to improve management programmes and further identify those areas which require priority conservation action.
Overall, fishing impacts and the increase of seawater temperatures are considered to be the largest threats to anthozoans in the Mediterranean region, in one way or another potentially affecting most or possibly almost all of the species present there. Globally, the conditions for calcified corals and gorgonians are predicted to get worse over the coming century with more frequent and severe mass mortality events expected due to increasing seawater
The gorgonian Eunicella cavolini in the Adriatic Sea. © Petar Kružić.